The present invention relates to a firewood chopper for producing chips, chopped firewood and the like employing a method where the wood material can be both cut and split during one and the same operation. The chopping material can consist of all kinds of small blocks and pieces of wood, such as lathes, branches, tree spires, slender trunks, etc. The chopper comprises a rotating or back-and-forth moving blade as well as a stationary counterblade, and the wood is chopped between the two blades.
The prior art contains several suggestions for choppers, which are intended for the chopping of small pieces of wood. Swedish patent publication No. 113 901 describes a chopper which is particularly suited for producing chips to be used in gas generators. This chopper includes a motor-run balance wheel, to which is hitched a cutting blade. The wood infeed gutter is placed in a slightly slanted position compared to the motion plane of the blade. The infeed gutter supports the wood from underneath while the rotating blade chops slices at its end. There are small splitting blades attached to the big cutting blade at right angles to it, which splitting blades simultaneously split the cut-off slices of wood.
One of the drawbacks of the above described arrangement is its comparatively great power demand. This is partly due to the fact that the chopping is carried out using a straight blade which is oriented almost vertically with respect to the wood fibres. In order to function satisfactorily the blade has to rotate at a comparatively high speed, and this increases the power demand. Moreover, by employing the above described arrangement it is hardly possible to produce, for example, chopped firewood pieces having the length of 35-50 cm so that the pieces are also split. The reason for this is the fact that the splitting blades are too small and wrongly placed for this purpose.
In the German patent publication Nos. 633 018 and 908 790 are introduced choppers which are also meant to be used in the production of chips for wood gas generators. The arrangement described in this publication comprises two oppositely rotating drums, on the outer surface of which are placed blades in a radial fashion. The rotating movement of the two drums is synchronized so that the pieces of wood are cut into suitable slices between the blades attached to the two opposite drums. Attached to each cutting blade there is also a splitting blade at right angles to the cutting blade, the purpose of which is to split the choppings simultaneously with the cutting operation.
In the latter publication is described a chopper which includes a blade which moves back and forth along a straight line, and a V-shaped guard plate. The blade is driven, for example, by a hydraulic cylinder. The cutting blade has splitting blades mounted at right angles to it.
The drawbacks of the above described arrangements include, among other things, their great cutting power requirements which also result in the need for structure to be massive and strong. Also, it is doubtful whether the device represented in the patent publication No. 908 970 could split the choppings in case their length should approach half a meter. This is due to the incorrect positioning of the splitting blades.